Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations are empty, so the description carries the full burden. It discloses critical behaviors: the tool is asynchronous (returns tool_job and status queued), requires polling get_tool_job_status, and has rate limits with per-file caps. It also clarifies the upload process and that complete_upload is not needed, which is non-obvious.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is fairly long but well-structured, with each section adding new information: purpose, prerequisites, async behavior, limits. It's front-loaded with the core purpose and free nature, then details. Could be slightly more concise, but every sentence earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's complexity (async, multi-step upload, rate limits), the description covers all necessary context: how to obtain the file, how to handle async, what output to expect, and limitations. No output schema exists, so the description explains the return value enough.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so parameters are already well-documented. The description reinforces count (1-10, default) and width (optional), but adds no new semantics beyond what's in the schema. Baseline 3 is appropriate as the description adds minimal value beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states what the tool does: extracts evenly-spaced thumbnail frames from an uploaded video file. It names the specific resource (video hashid) and the action, distinguishing it from sibling tools like edit_image or render_clip.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Provides explicit usage guidance: it explains the prerequisites (use create_upload, PUT bytes, pass id), what not to do (do NOT call complete_upload), and how to handle the asynchronous nature (poll get_tool_job_status). Also notes it's free compared to paid pipeline, giving clear context for selection.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.